Ancient stardust sheds light on the first stars

Thursday, March 9, 2017

The Atacama Large Millimetre/submillimetre Array, or ALMA, located high in the northern Chilean desert of Atacama released Wednesday (March 8) colorful images of a huge mass of glowing stardust of a galaxy stretch back from when the Universe was at its inception and only four percent of its present age.

This galaxy was observed shortly after its formation and is the most distant galaxy in which dust or oxygen has been detected. It could also shed light on the birth and explosive deaths of the very first stars.

The observation was carried out by an international team of astronomers, led by Nicolas Laporte of University College London.

The team spotted A2744_YD4 and then were surprised to find that this youthful galaxy contained an abundance of interstellar dust—dust formed by the deaths of an earlier generation of stars.

Follow-up observations using ESO’s Very Large Telescope confirmed the enormous distance to A2744_YD4. The galaxy appears as it was when the Universe was only 600 million years old, during the period when the first stars and galaxies were forming, according to the news release.

Cosmic dust is mainly composed of silicon, carbon and aluminium, in grains as small as a millionth of a centimetre across. The chemical elements in these grains are forged inside stars and are scattered across the cosmos when the stars die most spectacularly in supernova explosions, the final fate of short-lived, massive stars.

The detection of dust in the early Universe provides new information on when the first supernovae exploded and the time when the first hot stars bathed the Universe in light. Determining the timing of this “cosmic dawn” is one of the holy grails of modern astronomy, and it can be indirectly probed through the study of early interstellar dust, according to the news release.

ALMA has produced the sharpest pictures ever made at submillimeter wavelengths. ALMA’s telescope is situated in the remote Atacama desert in northern Chile, where dryness and altitude produce some of the best conditions possible on Earth for observing the night sky.

ALMA’s operations are led by the European Southern Observatory (ESO), the U.S. National Radio Astronomy Observatory and the National Astronomical Observatory of Japan.